I've just bought an HD6870 a month or so ago and did a huge amount of research on which was best for overclocking/cooling etc, and in the end I chose the HIS HD6870 IceQx Turbo 1gb
http://www.itreviews.com/hardware/graphics-cards/his-hd-6870-iceq-x-turbo-x/
There are a few iterations, mine had a small factory overclock of 920mhz gpu (900mhz stock) and 1120mhz mem (1050mhz stock) but more importantly, the awesome Iceq cooler (pretty much the best on the market) It has huge heat pipes and a superb fan setup, that is very, very quiet compared to some I've heard, even on full chat.
I set about overclocking mine pretty much straight away, and have managed to overclock it to the maximum settings (on afterburner and CCC) - so it is now running at 1000mhz gpu and 1250mhz mem! Which is a pretty excellent overclock. I've got the voltage running at 1.3v and have tweaked the fan profile to be a little more aggressive, the highest I have seen the temps rise with all these tweaks are 71 degrees after hours of play on BF3. I don't think I need the voltage quite so high, so am going to set about lowering it tonight, which should bring the temps down even more (not that they are high!)
I can't recommend this card highly enough, I bought mine from (sorry) ******, for £150 (although I have since checked and this card has disappeared from there and only the 6850 version is available.
On battlefield 3, I'm running eyefinity on 3 x 19" monitors, 3840x1024 resolution, mostly high settings, 16xAF, no AA and I get a really decent late 48-55 fps. With very little fluctuation.
Go for one, you wont be disappointed! Just hope you can still find one of the brilliant HIS Iceq cooler versions. I had the iceq version on my previous HD 4670 and that also overclocked superbly. Eventually I flashed a new bios to this card as it was rock stable at the overclock, I'll probably end up doing the same to this card in the near future! (more testing needed)
Hope this helps make up your mind!
